System Design and Scalable Application Architecture

You can build features. The blank page is the architecture: someone says "we need a real-time activity feed," or "support fifty times the users by next quarter," or an interviewer says "design a ride-hailing backend" — and the hard part isn't writing code, it's deciding what the pieces are and why. This course is about that decision. It gives you a method you can run on anything: pull out the real requirements, size them with back-of-the-envelope math, split the system into services with boundaries that hold, model the data and trace how it actually flows, then reach into a toolbox of reusable building blocks — load balancers, caches, replicas, shards, queues, consistent hashing, quorums, event streams — and place each one for a reason you can defend. You'll learn the trade-offs that decide real systems: SQL versus NoSQL by access pattern, fan-out on write versus on read, strong versus eventual consistency, why a partition forces you to choose, why "exactly-once" is really at-least-once plus idempotency. Then you'll compose those blocks into the architectures every team eventually builds — a read-heavy lookup service, a social feed, real-time chat, a media platform, a streaming aggregator, a booking-and-payments system that can't double-charge, a geo-proximity matcher. Because shipping isn't the end, you'll also design for failure, make a system observable with real SLOs, weigh security, multi-tenancy, and cost, and plan how an architecture migrates and grows instead of being rewritten. And because a design nobody understands is worthless, you'll finish by communicating it — clean diagrams, architecture decision records, and presenting under the clock, whether the audience is your team or an interview panel. Whether you're leading a team, founding a company, or preparing for system-design interviews, the underlying skill is the same: turning a vague requirement into an architecture you can stand behind.